Handling Intermittence: How to Survive Test Driven Development

http://joblivious.wordpress.com/2009/02/20/handling-intermittence-how-to-survive-test-driven-development/

by jmathes • 17 years ago

21 17 17 years ago

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CalmQuiet• 17 years ago

Although my projects are small and not currently using TDD, I found this analysis in systematizing development strategies. Present five ways of breaking down ways you set yourself up for intermittent failures during development:

Hidden data dependence

Race conditions

Time sensitive tests

Unstable 3rd party software

Intentional randomness in code.

lgriffith5• 17 years ago

TDD means you write your test before you write your code.

Test code is code. You must write test code for your test code before you can write your test code.

Test code for test code is code. You must write test code for your test code for your test code before you can write your test code for your test code.

TDD is trapped in a loop of infinite regression. This means that TDD never produces actual application code. In fact, it can't even produce test code. How do you define a test of a test of a test .... of a test ... of a test ..... so you can write it? You can't define it so you can't write it. You have no starting point.

The answer must be that you really cannot do TDD. You just call it TDD. At some level you rely on the old standby of clean simple design, incremental implementation, inspection, and manual testing. Why not cut to the chase and do that on your application code?

cellis• 17 years ago

You can put me in the downvote column, too. I happen to view TDD as a completely obnoxious and unnecessary exercise.

gjm114• 17 years ago

It's much easier to arrange for your test code to be extremely modular, with different bits not affecting one another, than it is for the actual application code. And for most problems it's much easier to get evidence that you've solved them right than it is to solve them right. (It's a bit like the difference between P and NP.) Therefore, writing good test code is much much easier than writing good application code. This is the answer to your last question, and the reason why the rest of what you said is wrong.

lgriffith5• 17 years ago

How do you know your test code is testing what you need it to test without actually testing it? If not by TDD, then are you really using TDD or simply saying that you are?

Like I say. Cut to the chase. Incrementally write good, clean, well designed, application code. Then inspect and manually test. THAT is the ONLY thing that really works. Stop pretending you are doing something that you aren't. Especially don't use it as an excuse for writing lousy, poorly designed, and poorly implemented application code.

TDD is still one more attempt to create a sacred Silver Bullet that gets good results without knowledge, skill, understanding, thought, discipline, or effort. Its at best a very feeble tool in a quiver of feeble tools. It takes a good, well trained brain, paying attention to get good results. Without that, nothing will work.

PS: Writing good code is never easy. It only looks easy when done by someone who really knows what they are doing.

jbert• 17 years ago

Because a failure in your test code means some application code isn't tested as well as it should be. It doesn't mean the application code will fail.

A failure in your application code can be much more serious.

Hence, in general, you test your application code, but not your test code.

jmathes2• 17 years ago

Each test you write is a value-add. You get increased safety that what you're testing works the way you think it does, and that it will continue to do so as people modify it. Not all cases need to be tested; "test to your level of paranoia" is our motto. In the case of tests themselves, the value add for testing individual tests has never been worth the ROI. There are, however, tests for the testing _system_, insofar as that's possible (which it is, for the most part).

As for the "I happen to view TDD as a completely obnoxious and unnecessary exercise" objection, I'd be willing to bet you've never tried TDD. It doesn't take long for proper TDD to _save_ you time. Each iteration cycle is slower, but the marginal cost for adding new code to a complex codebase doesn't increase nearly as much.

Without TDD, you soon have to spend time on manual testing, and then you've got humans in QE basically practicing TDD for you, as the walk through script after script doing things that could be done faster by a computer. The only time it's appropriate to consider skipping TDD, IMO, is on tiny one-man projects.

lgriffith5• 17 years ago

I see. TDD works on poorly designed, poorly implemented, basically lousy code. Code that is highly coupled, withlow cohesion, and is inappropriately modularized. This necessitates that all code must be tested every time there is a "modification". Add to that the random unthoughtful modifications made by careless programmers who have identified the wrong problem to fix and you get constant disaster.

I say, fix the fundamental problem by not writing lousy code in the first place. THAT would really be adding value rather than simply adding job security busy work. Automated testing cannot fix lousy code. Most of the time, it can't even discover it.

There is no magical way that gets good results without knowledge, skill, understanding, thought, discipline, and effort. With those things, all you need are good enough tools. TDD may be one of those good enough tools in some limited circumstances. It is not a Silver Bullet that cures all, most, or even many software flaws.

Keep in mind that one really good programmer can out produce a team of twenty poor programmers. Also keep in mind that one poor programmer can keep twenty really good programmers busy cleaning up the trash they create.

TDD is a very poor band aid used to cover up an even more fundamental problem: most programmers are lousy at programming. That is the problem that need fixing.

crescendo• 17 years ago

I think you've missed the point. The real utility of coding to pass a test is not to verify the current state of the application. You can easily cross check that you're getting the right return values from any module manually. The real beauty of TDD comes a few months down the road when you've forgotten the current module, and you make some change that affects it. With a unit test framework in place, regression problems like these are found immediately.

speek• 17 years ago

As much as TDD irks me to think about when I'm in the middle of a program, it's a very useful thing.

Its saved me from making countless mistakes.

JUnit isn't good for beginners though, because you have to define an equals method for each class. Not only is that completely repetitive, but it is also very difficult for beginning programmers to write good tests. If you haven't been programming for very long, how do you know how to define equality? Do you consider two objects that have the same fields (only the fields you're testing) to be equal? Or are you checking whether or not two objects are the same (bit for bit in the stack)? What happens when you have super-classes that have less fields than their subclasses?

Anyway, one of my professors is working on a new tester for java (http://www.ccs.neu.edu/javalib/Tester/index.html). It's very elegant; the syntax is very clean:

"public void testGresterThan(Tester t){

     t.checkexpect(7 > 4, true);

Handling Intermittence: How to Survive Test Driven Development

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